I've used the pack on singletrack, fire road and bike park for quite a few days now. It's held everything I've needed to carry (tools, food, extra layers, helmet, armour) and the weight distribution has been great. You can strap all the external gear (armour and helmet) down firmly so it doesn't get in the way on the pedal up. The organisational pockets are a god-send, and much better than my previous Nalgene pack. The slim, bike-tailored fit is very nice for ventilation. The hydration pack is good, but it would be nice if the valve was a bit simpler to open. It's impossible to do one-handed while riding on singletrack, and the bladder has tasted a bit like chemicals a couple of times. Hopefully this will dissipate with time though.